1. Field of the Invention
The invention generally relates to a damper disk assembly. More specifically, the present invention relates a damper disk assembly for absorbing and damping torsional vibrations in a power transmission system.
2. Background Information
A damper disk assembly often used in a clutch disk assembly of an automobile. The damper disk assembly is formed of an input member, an output member and a damper mechanism. The input member can be coupled to an input flywheel. The output member can be coupled to a shaft extending from a transmission. The damper mechanism elastically couples the input and output members together in a rotating direction. The input member is typically formed of a pair of friction facings and a pair of input plates which are arranged radially inside the friction facings. The friction facings are fixedly coupled to one of the input plates. The output member is typically in the form of a hub that is nonrotatably coupled to the shaft of the transmission. The hub has a centrally located boss with a splined bore, and a radial flange extending outwardly from the boss. The splined bore of the boss is spline-engaged with the shaft of the transmission. The radial flange extends from the boss and is elastically coupled to the input plates by the damper mechanism. The damper mechanism is formed of springs which elastically couple the pair of input plates to the flange of the hub in the rotating direction, and a friction generating mechanism for generating friction between the pair of input plates and the flange. When the pair of input plates rotates relatively to the hub, the springs are compressed in the rotating direction so that sliding occurs in the friction generating mechanism. As a result, torsional vibrations in the rotating direction are absorbed and dampened.
The flange of the hub is provided with windows (spring accommodating apertures) for receiving the springs therein. The paired input plates are provided with spring support portions (spring accommodating portions) for supporting the springs. Each window supports the circumferentially opposite ends and radially opposite ends of the spring. The spring support portions support the circumferentially opposite ends, radially opposite ends and axially opposite ends of the spring. When the input plate pair rotates relatively to the flange, each spring is compressed between one end surface on one circumferential side of the window and one end surface on the other circumferential side of the spring support portions. In this compressing operation, each of the end surfaces on circumferential opposite sides of the window and the spring support portions move such that the radially outer portions of these surfaces move a distance that is circumferentially longer than the radially inner portions of these surfaces. Therefore, each spring has such a form that the radially outer portion (i.e., the outer portion in the radial direction of the disk) has a circumferential length or width shorter than that of the radially inner portion. When the spring is compressed in a nonparallel fashion as described above, the spring is subjected to a bending force in addition to a shearing force, resulting in a reduced lifetime.
An elastic float arranged within a coil spring has been known as a kind of spring arrangement within the window and the support portion. The elastic float is, for example, a cylindrical or columnar member having a rubber member with hard resin members arranged on the opposite sides of the rubber member, respectively. The elastic float can freely move in predetermined angles between circumferentially opposite ends of the window and spring support portion when the damper disk assembly is in a free state. The elastic float is compressed between the end on circumferentially one side of the window and the end on the circumferentially other side of the spring support portion after the coil spring is compressed to a certain extent. Consequently, the rigidity of the damper mechanism rapidly increases. In this manner, the elastic float achieves a stop torque in the damper disk assembly.
However, when the coil spring is compressed in the nonparallel fashion as already described in connection with the prior art, the elastic float inclines due to the coil spring. Thus, the elastic float is compressed so that a situation can occur in that the end surface of the elastic float is only in partial contact with the other member (the end surface of the plate member or the spring seat). In this case, the elastic float cannot generate a sufficiently large load, and therefore, a desired stop torque cannot be obtained.
In view of the above, there exists a need for a damper disk assembly which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.